The present invention relates to a variable valve timing apparatus for use in a four-cycle internal combustion engine, and more particularly, to a type thereof capable of selectively shifting valve timing between low speed and high speed regions.
According to a conventional valve timing apparatus, a rocker arm disposed between a camshaft and an intake or exhaust valve has a shiftable pivot point to alter valve timing. Alternatively, a plurality of rocker arms are provided to selectively actuate one of them to change valve timing. In both cases, the resultant structures become complicated and complex.
Further, the rocker arm is normally provided with a means for adjusting a tappet clearance such as an adjusting screw. With this construction, the position of the adjusting means may determine the length of the rocker arm. Therefore, suitable positional relationship between the rocker arm and the adjusting means has been investigated. Sometimes, the position of the adjusting means causes the length of the rocker arm to be long, so that compact and light-weight structure may not be obtainable.